1. Field of the Invention
The present invention relates to a light emitting device, a light emitting device with, for example, a light emitting diode as a light source, and an illuminating device using the same.
2. Background Art
In recent years, as light sources (light emitting devices) of external illuminating devices such as tail lamps, stop lamps and headlights mounted to automobiles and the like, instead of conventional electric bulbs having filament, LED lamps with light emitting diodes (Light Emitting Diodes) incorporated therein are frequently used. An LED lamp has the advantages of long life, low heat generation, low power consumption and space saving, and from these characteristics, the LED lamp gives the merits such as maintenance free and improvement in fuel efficiency when it is applied to an on-vehicle lamp.
Incidentally, with respect to the external illuminating devices mounted to automobiles and the like, the irradiation direction, the illuminance distribution and the like are strictly defined for the reason of the safety standards as an automobile. Even when the light source is replaced with the LED lamp, the similar characteristics are required. When a conventional electric bulb having filament is used as a light source, the light source can be regarded as a substantially point light source, and the radiation light is uniformly emitted in all directions. Therefore, it has been easy to control the light distribution characteristics of the illuminating device by using an external reflecting mirror. In contrast with this, when an LED lamp is used as the light source, it is basically difficult to design and control the light distribution characteristics in the illuminating device using an external reflecting mirror. This is because an LED lamp has less light emitted downward from the mounting surface of the light emitting element and has the property that brightness differs depending on the emission direction, due to the structure in which the light emitting element is mounted on the metal to be a lead. Further, the external illuminating device mounted to an automobile or the like has the limitation in design such as the size of the external reflecting mirror or the like, and this also becomes one cause to increase difficulty of design.
The illuminating device in which a light emitting diode is incorporated is described in, for example, Japanese Patent Laid-Open No. 2005-64145. The illuminating device enhances utilization efficiency of light by causing the light which is irradiated from a light emitting diode to a light emission range ox to be incident on a lens called a dimming body, and causing the emission light to go out from the outgoing surface of the lens.